It is known to transmit power over data lines to power remote equipment. Power Over Ethernet (PoE) is an example of one such system. In PoE, limited power is transmitted to Ethernet-connected equipment (e.g., VoIP telephones, WLAN transmitters, security cameras, etc.) from an Ethernet switch. DC power from the switch is transmitted over two twisted wire pairs in the standard CAT-5 cabling. One or both of the wire pairs also transmit differential data signals, since the DC common mode voltage does not affect the data. In this way, the need for providing any external power source for the Powered Devices (PDs) can be eliminated. The standards for PoE are set out in IEEE 802.3, incorporated herein by reference. In PoE, the Power Sourcing Equipment (PSE) supplies the same standardized voltage to every type of PD sufficient to ensure that the PD receives at least 37V, despite unknown voltage drops along the wire pairs.
A newer technology is Power Over Data Lines (PoDL) where power is transmitted over a single, twisted wire pair along with the differential data. As of the date of this disclosure, the IEEE is in the process of receiving comments to develop standards for PoDL as IEEE P802.3bu. PoDL may be more flexible than PoE and, since it requires one less wire pair, is likely to become a popular technique, especially in automobiles.
It is envisioned that most future applications of PoDL will require some sort of handshaking between the PSE and the PD before the full power/voltage is applied to the data lines by the PSE. This is because different types of PDs may need different voltage levels, different maximum power levels, or not be PoDL-compatible. Other information may also be conveyed during the handshaking.
Such handshaking may consist of a low power/voltage signal being generated by the PSE on the wire pair, and the PD may respond in a characteristic way to identify to the PSE that the PD is PoDL-compatible (typically called a detection signature) as well to identify voltage and power requirements (typically called a classification signature), among other information.
In an automobile application for PoDL, for instance, the types of PSEs and PDs may be highly regulated by the automobile manufacturer. This allows various innovative and customized techniques to be used for the detection and classification schemes.
Thus, what is needed are various possible detection and classification schemes for PoDL that can be applied for different applications.